Plate Tectonics Theory *The lithosphere (upper mantle) is divided into plates Tectonic Plate=Lithosphere The asthenosphere (lower mantle) is the soft, weak layer that the lithosphere lays on

Convection Currents Plate motion is caused by convection currents in the mantle from heat within the Earth

Plate Tectonics Theory

Plate Boundaries All major interactions among individual plates occur along their boundaries 3 main types of plate boundaries:

Plate Boundaries 1. Divergent : 2 plates move apart

Divergent Boundaries Most are located along the crests of oceanic ridges Where new ocean crust is created

Seafloor Spreading The age of the seafloor is youngest at the mid ocean ridge and gets older as you move away

Plate Boundaries 2. Convergent Boundaries: 2 plates move together (crust destroyed)

Plate Boundaries Subduction: Heavier plate sinks below lighter plate into mantle & melts

Subduction Zone The boundary where 2 plates collide

Types of Convergent Boundaries 1. Oceanic-Oceanic= Volcanic Island Arcs

Trench: Topographic depressions on the sea floor

2. Oceanic-Continental= Continental Volcanic Arcs

3. Continental-Continental=Mountains

Plate Boundaries 3. Transform Boundaries: 2 plates grind past each other (earthquakes occur) and does not create or destroy crust